This invention relates generally to circuits for converting light into electricity and more particularly to those of the type usable on cameras for automatic exposure control.
In a photoelectric conversion circuit in which a photo sensor, for example, a photodiode, is employed, an electric charge is stored in the photodiode because of its junction capacitance when a source of power supply is applied in the circuit for operation and conventionally such electric charge can only be discharged by the photo-output current of the photodiode. Because of this, particularly in the case where the illumination at the light-receiving area is so limited as to cause the photodiode to produce an output current of an order of pico-ampere, a considerable length of time has been required for the circuit output to reach the level corresponding to the given photo-output current and this has involved a disadvantage that the circuit can operate only with a correspondingly extended response time.